A new stair‐band hysteresis current control with constant switching frequency for UPFC application

Abstract A new approach based on the hysteresis current controller to obtain a constant switching frequency is proposed. This method generates an adaptive stair‐band by tracking changes in the reference current and accounting for the number of converter voltage levels. To achieve this, the maximum and minimum values of the fixed‐band switching frequency of the conventional hysteresis and their correspondence with the reference current were first determined. The proposed approach solves the problem of the variable frequency of the conventional hysteresis controller while retaining its simplicity. It also eliminates the need for intensive online adaptive band calculations, while preserving its efficiency. Furthermore, it can be applied to multi‐level converter topologies, where using a hysteresis controller has historically been challenging. To validate the proposed method, it was applied to the unified power flow controller (UPFC) with a three‐level neutral‐point clamped converter topology that connects two high‐voltage power networks in Cameroon. Simulations conducted in SIMULINK showed quasi‐constant switching frequency and accurate tracking of reference currents in both the shunt and series converters of the UPFC. This innovative approach offers an alternative solution for integrating intermittent energy sources, enhancing the UPFC's dynamic capabilities in managing diverse energy sources.